In U.S. Pat. No. 2,903,162, Regan discloses a winding key for collapsible wall containers. These plastic or metal containers are commonly used for dispensing fluid and semifluid materials, such as toothpaste, shampoo, glue, lotions, medicines and cake frosting. Winding keys are desirable because they reduce waste of the tube contents, indicate the degree of fill in a tube and provide a neater tube appearance.
The winding key of Regan comprises a blank which has been punched or cut from a metal sheet and bent to have projecting longitudinal flanges. The flanges form therebetween a longitudinally-extending slot adapted to receive the flat tube end. At one end of the key, a handle is formed for manually rotating the key about its longitudinal axis, and thus winding the lower end of the tube. Pivotally connected to the key is a rigid retaining bar of a U-shaped configuration and having a pair of parallel legs joined at their extremities furthermost from the pivotal connection by a transverse portion. The extremities of the legs closest to the pivotal connection are bent inwardly and extend through oppositely aligned openings in the key. The retaining bar is thus pivotally connected to the body of the key by the cooperation of the inwardly directed extremities with the oppositely aligned openings of the key. A flange of the key is bent upwardly to abut the ends of the longitudinal flanges, and has a tongue adapted to receive and positively engage the transverse portion of the retaining bar when the bar is in its locking position. The retaining bar will then engage the container wall to oppose the restoring force inherent in the tube material which tends to cause unwinding.
Devices of the type described are quite useful, but have not found widespread acceptance because the cost of the winding key is significant compared to other manufacturing costs, such as the cost of the tube and its filling.
An object of the invention is to produce a winding key for collapsible tubes having simplified construction, which is durable and easy to use.